transcript: clamp long user messages with a more…/less… toggle

Pastes over 1200 chars collapse in the bubble; copy still gets the full text.

surfaces/gui/e2e/chat.spec.ts

@@ -57,3 +57,37 @@ test("approval: Deny skips the tool and the agent says so", async ({ page }) =>
   await page.getByRole("button", { name: "Deny" }).last().click();
   await expect(page.getByText("Understood — skipped the command.")).toBeVisible();
 });
+
+test("long user pastes clamp with a more…/less… toggle", async ({ page }) => {
+  await page.goto("/");
+  const box = page.getByPlaceholder(/Ask the coworker/);
+  await expect(box).toBeVisible();
+
+  const tail = "END-OF-PASTE-MARKER";
+  const paste =
+    "reply OK. " + "lorem ipsum dolor sit amet consectetur ".repeat(60) + tail; // ~2.4k chars
+  await box.fill(paste);
+  await page.getByRole("button", { name: "Send" }).click();
+
+  // Clamped: the bubble shows the head but not the tail, plus the toggle.
+  const more = page.getByRole("button", { name: "more…" });
+  await expect(more).toBeVisible();
+  const bubble = page.locator(".bubble-user").last();
+  await expect(bubble).toContainText("reply OK.");
+  await expect(bubble).not.toContainText(tail);
+
+  // Expand → full text + "less…"; collapse → clamped again.
+  await more.click();
+  await expect(bubble).toContainText(tail);
+  const less = page.getByRole("button", { name: "less…" });
+  await expect(less).toBeVisible();
+  await less.click();
+  await expect(bubble).not.toContainText(tail);
+
+  // Short messages never show the control.
+  await expect(page.getByText("Echo:").first()).toBeVisible();
+  await box.fill("short follow-up");
+  await page.getByRole("button", { name: "Send" }).click();
+  await expect(page.getByText("short follow-up", { exact: true }).first()).toBeVisible();
+  await expect(page.getByRole("button", { name: "more…" })).toHaveCount(1); // still only the paste's
+});

surfaces/gui/src/components/Transcript.tsx

@@ -6,6 +6,28 @@ import { Markdown } from "./Markdown";
 import { ConnectorMessageCard } from "./ConnectorMessageCard";
 import { Icon } from "./Icon";
 
+// Long user pastes swallow the transcript (owner ask 2026-07-30): clamp past a generous
+// threshold with a more…/less… toggle. Normal typed messages never see the control; the
+// full text still drives copy (BubbleMeta) and is what the model received.
+const USER_CLAMP_CHARS = 1200;
+
+function ClampedUserText({ text }: { text: string }) {
+  const [open, setOpen] = useState(false);
+  if (text.length <= USER_CLAMP_CHARS) return <>{text}</>;
+  return (
+    <>
+      {open ? text : text.slice(0, USER_CLAMP_CHARS).trimEnd() + "…"}
+      <button
+        type="button"
+        onClick={() => setOpen((o) => !o)}
+        className="block mt-1.5 text-[12.5px] font-medium underline underline-offset-2 opacity-75 hover:opacity-100"
+      >
+        {open ? "less…" : "more…"}
+      </button>
+    </>
+  );
+}
+
 // Hover affordances for a message bubble (FB-005): copy the raw text + the message's time.
 // Lives in a ZERO-HEIGHT strip under the bubble (absolute, inside the transcript's 20px gap)
 // so revealing it on group-hover never shifts the layout. `ts` is unix seconds — canonical
@@ -398,7 +420,7 @@ export function Transcript({ items, running, streamingText, onRetry }: Props) {
                       )}
                     </div>
                   )}
-                  {item.text}
+                  <ClampedUserText text={item.text} />
                 </div>
                 <BubbleMeta text={item.text} ts={item.ts} align="right" />
               </div>